Method and apparatus for rolling tubes

ABSTRACT

A tube mill and a method of rolling tubes in which tubular workpieces are supported by a mandrel as they pass through a series of roll stands that have grooved rolls that reduce the wall thickness and greatly elongate the workpieces during their passage through the mill. The movement of the mandrel is controlled to distribute wear on the mandrel throughout a substantial area and to facilitate entry of the workpieces into the mill. The mandrel is periodically rotated to distribute wear on the mandrel. A construction is provided for quick interchange of mandrels. The positions of the mandrel and the workpiece are indicated to the operator during the rolling operation so that he can change the operation of the mill if that is desirable.

United States Patent 72 Inventor William Rndder Pittsburgh, Pa. (21]Appl. No. 744,366 [22] Filed July 12, 1968 [45] Patented July 20, 1971[73] Assignee Slaw-Knox Company Pittsburgh, Pa. Continuation-impart ofapplication Ser. No. 432,597, Feb. 15, 1965, now Patent No. 3,392,565.

[54] METHOD AND APPARATUS FOR ROLLING TUBES 14 Claims, 29 Drawing Figs.

[52] US. Cl 72/209 [51] 1nt.C1 B21b 17/10 [50] Field of Search 72/208,209, 201, 367, 368, 370,120,428

[5 6] References Cited UNITED STATES PATENTS 970,263 9/1910 Peters72/209 988,834 4/1911 Stiefel 72/209 1,100,696 6/1914 Offutt 72/2092,261,937 11/1941 Kelso 72/209 2,356,734 8/1944 Bannister 72/2092,778,253 1/1957 Brownstein. 72/209 3,112,661 12/1963 Coe 72/2083,267,718 8/1966 Grube 72/208 3,394,568 7/1968 Calmesu... 72/2093,392,565 7/1968 Rodder 72/201 Primary Examiner- Richard J. HerbstAttorney-Bosworth, Sessions and Herrstrom and Cain ABSTRACT: A tube milland a method of rolling tubes in which tubular workpieces are supportedby a mandrel as they pass through a series of roll stands that havegrooved rolls that reduce the wall thickness and greatly elongate theworkpieces during their passage through the mill. The movement of themandrel is controlled to distribute wear on the mandrel throughout asubstantial area and to facilitate entry of the workpieces into themill. The mandrel is periodically rotated to distribute wear on themandrel. A construction is provided for quick interchange of mandrels,The positions of the mandrel and the workpiece are indicated to theoperator during the rolling operation so that he can change theoperation of the mill if that is desirable.

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METHOD AND APPARATUS FOR ROLLING TUBES CROSS-REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-part of copending application Ser. No. 432,597, filed Feb. 15, 1965, U.S. Pat. No.3,392,565, issue date July 16,1968. 7

BACKGROUND OF THE INVENTION This invention relates to the manufacture ofseamless metal tubing and more particularly to an improvement or furtherdevelopment of the plug or mandrel mill and the methodof rolling tubularblanks over a mandrel to reduce their wall thicknesses and diameters andgreatly to elongate them that is disclosed and claimed in my aforesaidcopending application.

That application discloses a method and apparatus for rolling piercedshells or like workpieces in which many of the problems inherent in theconstruction and operation of a conventional plug mills and fullfloating mandrel mills are ob viated as explained more fully therein.Briefly, that application discloses a plug or mandrel mill embodyingaplurality of roll stands, so that substantial reduction in wallthickness and diameter and consequent substantial elongation of theworkpiece can be obtained. An elongated internal plug or mandrel is usedin combination with the roll stands, and the motion of the mandrel iscontrolled so that the mandrel moves with respect to the roll stands andthe workpiece. The motion vof the mandrel is controlled by a hollowmandrel rod to which the mandrel is secured and through which a coolingfluid is circulated so that the mandrel is maintained at .a reasonabletemperature and can be used for long periods of time withoutreplacement. The movement of the mandreldistributes the wear throughouta large pan of the length of the mandrel, gives lubrication during therolling operation, and gives a better finish to the interior of the tubethan can be obtained in conventional plug and floating mandrel mills.

It has also been proposed to control the movement of mandrels in mandrelmills at the initial stage of the rolling operation as shown in thepeters Peters Pat. No. 970,263. A mill in which the mandrel is withdrawnfrom the tube in a direction opposite to the direction of the movementof the tube through the mill is shown in the Peters U.S. Pat. No.954,880. Other patents showing efforts to improve the tuberollingmillsare French Pat. No. 1,322,304, in which the controlof the movementof a mandrel with respect to a mill is suggested, and French Pat. No.1,224,862, which utilizes a stepped mandrel that may be permitted toadvance slightly during rolling. These patents, however, do not presentpractical solutions to the problems solved in my aforesaid application.

SUMMARY OF THE INVENTION A general object of the present invention isthe provision of a mill for rolling tubular workpieces such as piercedshells and a method of operating the mill in which many of the problemsinherent in the construction and operation of conventional plug millsand mandrel mills of the type heretofore known are obviated. Morespecific objects are to provide a mandrel mill embodying a plurality ofroll stands (a multistand" mill) and a method of operating the samewherein the movement of the mandrel is controlled to facilitate theentry of the pierced shell into the mill; the provision of a multistandmandrel mill in which the mandrel is rotated as well as;movedlongitudinally to distribute the wear on the mandrel and increase thelife of the mandrel; the provision of a multistand mandrel mill in whichmandrels can be changed with comparative rapidity when necessary becauseof wear or in order to accommodate different sizes of tubing; theprovision of a multistand mandrel mill in which the operator is given anindication of the position of the mandrel with respect to the millduring the operation of the mill, and the provision of a multistandmandrel mill in which the operator receives an indication of both theposition of the mandrel and the position of the workpiece during theoperation of the mill.

Briefly, the above and other objects of the invention are attained by (Ithe provision of a mechanism for controlling the movement of the mandrelthat is arranged to advance the mandrel, preferably at approximately thesame speed as the speed of the tube leaving the first roll stand, at theinstant that the shell is entered into the first roll stand, therebyfacilitating entry of the shell into the-roll stand and reducing shockon the mechanism; (2) the provision of a mechanism that rotates themandrel a fraction of a turn between successive rolling operations,thereby to distribute circumferentially the wear on the mandrel; (3) theprovision of a quickly detachable connection between the mandrel properand the mandrel supporting bar so that mandrel or plugs can beinterchanged with rapidity and the connections for cooling fluid andlubricant, if any, being made automatically at the time that themandrels are interchanged, and (4) the provision of an indicatordisposedat the operators station orconsole and actuated by the mandreladvancing and retracting mechanism that shows the position of themandrel with respect to the mill at all times. Preferably, the positionof the shell in the mill is also indicated on the operator's console..These indications make it possible for the operator to vary the rate ofmovement of the mandrel with respect to the mill if that should appearto be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which illustrate apreferred form of the-invention:

FIGS. IA, lB'and 1C taken together constitute a top plan view somewhatdiagrammatically showing an apparatus embodying the present invention;

FIGS. 2A, 2B and 2C taken together constitute a somewhat diagrammaticside elevational view of the apparatus of FIG. 1;

FIG. 3 is an end elevational detail showing a stripping mechanism, theview being taken generally as indicated by the line 33 on FIG'. 2A;

FIG. 4 is a side elevational view on an enlarged scale illustrating thecarriage that supports the rear end of the mandrel bar; 1

FIG. 5 is a horizontal sectional view taken as indicated by line 5-5 ofFIG. 4;

FIG.'6 is an end view of the carriage that supports the rear end of themandrel bar showing the mechanism for rotating the mandrel bar;

FIG. 7 is a partial sectional view taken as indicated by-Iine 7-7 ofFIG. 6;

FIG. 8 is a partial sectional view on an enlarged scale taken on line8-8 of FIG. 2B and illustrating thepusher for pushing a workpiece intothe mill;

FIG. 9 is a fragmentary sectional view taken along line 9-9 of FIG. 2Band illustrating a stop for restraining a shell against movement towardthe mill while the mandrel is being passed through it;

FIG. 10 illustrates the mandrel and its supporting mandrel bar;

FIG. 11 is a sectional detail showing the quick disconnect connectionbetween the mandrel and the mandrel bar;

FIGS. 12 and 13 are sectional views on an enlarged scale taken on lines12-12 and 13-13 of FIG. 11, respectively;

FIG. 14 is a hydraulic circuit diagram showing a hydraulic system forcontrolling the mandrel movement;

FIGS. l5, l6, 17, I8 and 19 are diagrams illustrating successive stepsin the rolling of a tubular blank on the apparatus and according to thepreferred method;

FIGS. 20, 2I, 22 and 23 are diagrams showing the relative positions ofthe shell and mandrel during the rolling sequence, starting with theshell and ready to enter the first roll stand as shown in FIG. 20 andconcluding with the rolling operation having been completed as shown inFIG. 23;

FIG. 24 is a velocity diagram indicating the speed of the shell atvarious stages in its passage through the mill; and

FIG. 25 is a velocity diagram illustrating the speed of movement of themandrel at corresponding times during the rolling operation.

General Arrangement: As shown particularly in FIGS. 1A, 1B, 1C, 2A, 2Band 2C, an apparatus embodying the present invention is generallysimilar to the apparatus illustrated and described in my copendingapplication aforesaid and comprises a mill indicated in general at 5 andhaving roll stands 6, 7, 8, 9, l0 and 11 in which the actual reductionand elongation of the workpieces W takes place. The workpieces areordinarily in the form of pierced shells that are produced by a piercingmill (not shown). They are deposited on a receiving table indicated at12 and from this are transferred to an inlet table 13 which supports theworkpieces W in alignment with and immediately adjacent the inlet end ofthe mill 5. A shell or workpiece W, which is broken away to permitillustration of the receiving table, is shown in position on thereceiving table in FIGS. 1A and 1B. A portion of the mandrel over whichthe workpiece W are rolled is shown at 14 in FIGS. 1C, 28 and 2C, buthas been omitted from other figures for convenience of illustratingother components. The mandrel 14 is supported by a mandrel bar 15 and isadvanced and retracted by a mandrel thrust block 16 that is supported bya carriage 17 on extension 18 of the inlet table. The carriage is movedtoward and away from the mill on tracks 42 to advance and retract themandrel. The mandrel 14 is movable from a position in which its forwardend projects entirely through the mill to a position in which theforward end is retracted far enough from the entry end of the-mill topermit the inlet table to receive a shell to be rolled.

During the actual rolling operation the mandrel thrust block 16 engagesa mandrel movement control beam 19 that is also mounted for movement onthe table extension 18, and which controls the motion of the mandrelwithin the mill immediately before and during the rolling operation. Atube pusher mechanism indicated generally at 20 is utilized to engagethe rear end of a shell W that is in position on the inlet table 13 andto push the front end of the shell W into the first roll stand 6 of themill 5. Lubricant may be sprayed on the exterior of the mandrel by aspray box 20a located between the pusher and the front end of themandrel when the mandrel is in extreme retracted position. The pusher 20is of different construction from the pusher shown in. my copendingapplication and is described below. Thereafter the tube is drawn throughthe mill by the action of the rolls; the friction of the tube on themandrel 14 tends to draw the mandrel bar and associated mechanism alongwith the tube. This motion, however, is controlled by the mandrelmovement control beam 19, as described below. After passing through themill, the workpiece, which has been much elongated is discharged onto anoutlet table 21, only a fragment of which is shown in the drawings.

In order to prevent rolled workpieces that stick to the mandrel frombeing drawn back toward the mill when the mandrel is withdrawn, astripper mechanism 22, shown in FIG. 3, is disposed between the lastroll stand 11 and the outlet table 21. This comprises a stripper plate23 having a U-shaped recess 24 in its upper edge, the recess being largeenough to receive the mandrel 14 but small enough to block movement of arolled tubular workpiece through it. The plate 23 is raised and loweredby a fluid pressure cylinder 25 and is supported and guided by itsmovement by a guide 26. In use, if it appears that a rolled workpiecehas stuck to the mandrel, the operator actuates the cylinder 25 to raisethe stripper plate 23 to the position shown in broken lines in FIG. 3after the trailing end of the workpiece has passed beyond the plate 23.The mandrel is then withdrawn by mechanism described below. The plate 23blocks rearward movement of the workpiece and continued movement of themandrel in the rearward or withdrawing direction results in the releaseand stripping of the workpiece from the mandrel. The plate 23 is thenlowered preparatory to the rolling of the next workpiece.

The Mill: The mill proper is shown as being made up of six independentlydriven roll stands 6, 7, 8, 9, l0 and 11. The roll stands themselves maybe of conventional construction, each embodying a pair ofrolls 6', 7',8, 9', l0 and 11', as shown in FIGS. 15 to 19. The rolls are grooved asshown, but for convenience of illustration the rolls are shown in thesefigures in elevation and as being disposed on horizontal axes; however,as illustrated in my copending application, aforesaid, the axes of therolls are preferably at angles of 45 to the horizontal and the aces ofthe rolls in successive stands are at to each other as is the usualpractice in tube rolling mills of various types.

The rolls and the roll stands are driven by drive mechanisms 6, 7", 8",9", 10" and ll"'which are indicated diagrammatically inasmuch as theymay be of conventional construction. The mill is described in somewhatgreater detail in my aforesaid copending application and thisdescription will not be repeated herein. It is pointed out, however,that the peripheral speed of the rolls must progressively increase fromroll stand 6 through roll stand 9 because of the progressive elongationof the workpiece as it passes through the mill; as in any continuousrolling process the product of the cross-sectional area of tube and tubevelocity must have the same value in each roll stand. The lasttwo rollstands round up the work and, in the usual operation of the mill, stripthe work from the mandrel.

Receiving, Inlet and Outlet Tables: Except for the manual control andtube pushing mechanism which are described in greater detail below thereceiving, inlet and outlet tables 12, 13, and 21, respectively) are ofsimple and more or less conventional construction. They are, in general,similar to the corresponding parts disclosed in my said copendingapplication and their operation is as described therein. workpieces Ware deposited upon the rollers 30 of the receiving table 12 and aretransferred from the receiving table 12 to the inlet table 13 by aseries of kick-out arms and bars 32. While on the inlet table theworkpieces are supported by rolls 33.

The inlet table is also provided with a shell stop 35 (see FIGS. 1A, 18,2A, 2B and 9) that consists of a transversely extending member 36 havinga U-shaped groove in it dimensioned to surround the mandrel 14 as shownin FIG. 9 but to engage the end of a workpiece that is resting on therolls 33 of the inlet table 13. The member 36 is supported on atransverse shaft 37 and holds the tubular workpiece againstmovementtoward the mill during the time that the mandrel is being passed throughthe workpiece and into the mill. The shaft 37 is rotated by a fluidpressure cylinder and piston mechanism 38 and'crankarm 39 to move themember 36 out of the way when it is desired to advance a workpiece intothe mill, and is rotated in the opposite direction to return the memberinto the position shown in the drawings before the mandrel is advancedthrough another workpiece.

Mandrel Bar, Thrust Block and Carriage: As mentioned above, mandrel 14is positioned by the elongated mandrel bar 15 to which it is connectedby a coupling as indicated at 41 in FIGS. IC and 2C. Coupling 41 isshown in detail in FIGS. 10 to 13 and is described below. The rear endof the mandrel bar 15 is carried by the mandrel thrust block 16 which ismounted on carriage 17 that operates of tracks 42 on the table extension18. The rolling forces exerted by the operation of the mill tend to drawthe mandrel 14 through the mill. Since the rear end of the mandrel bar15 is secured to the mandrel thrust block 16, the substantial forcesexerted by the mandrel during rolling subject the mandrel bar only tostresses in tension. In order to transmit the tension forces from themandrel bar 15 to the mandrel thrust block 16, the end of the mandrelbar 15 is threaded to a coupling member 43 as shown particularly in FIG.5. This member is retained against longitudinal movement by a splitsleeve 44 that in turn engages an internal flange 46 on the mandrelthrust block 16 that is supported by trunnions 48 in the side members 49of the carriage 17.

The coupling member 43 extends rearwardly through the central opening ofthe mandrel thrust block 16 and is supported for rotation with respectto the mandrel thrust block not only by the, split sleeve 44 by also bya bearing 50. The bearing 50 is secured in place and the coupling member43 is held against rearward (away from the mill) longitudinal movementwith respect to the mandrel thrust block 16 by a plate 51 that is boltedto the mandrel thrust block and by spacer sleeves S2 and 53.

In order to move the carriage 17 toward and away from the mill andcorrespondingly to advance and retract the mandrel bar 15 and mandrel14, a cable drive mechanism for the carriage as shown in FIGS. 18, 1Cand 2B and 2C is preferably provided. This mechanism comprises a cable55, the ends of which are secured to opposite ends of the carriage 17,as shown, in FIG. 4, a spring 56 being interposed in the connection toreduce shocks. The cable passes over an idler pulley 57 at the forwardend of the inlet table extension 18 and several turns of the cable arewrapped around a driving drum 57 at the rear end of the table extension.

The drum 58 is arranged to be driven in either direction by a motor 59through a coupling 60. The motor, which is of a known type, iscontrollable to operate at continuously variable speeds in eitherdirection so that the carriage 17 can be advanced rapidly toward themill to pass the mandrel 14 through the workpiece and into properposition for rolling and slowed down just before the mandrel thrustblock 16 engages the mandrel movement control beam 19 to reduce shock.The motor 59 can also be operated to withdraw the mandrel 14 rapidlyfrom the rolled shell and the mill and back to a position wherein a newworkpiece can be positioned between the forward end of the mandrel andthe mill on the inlet table 13, The motor 59 can also be operated in theforward direction to exert a constant or substantially constant torqueso as to retain the mandrel thrust block 16 firmly in engagement withthe mandrel movement control beam 19 when the mandrel movement controlbeam 19 is stationary or is being advanced and before the workpiece isengaged with the first coil stand. This is described below in thesummary of the operation of the apparatus.

Cooling liquid is supplied to the interior of the mandrel 14 through aconduit 62 (FIGS. 4 and 5) that extends from a swivel fitting 63 at therear end of the coupling member 43 to a position adjacent the forwardend of the mandrel 14. As in the case of my copending application, fluidis discharged through conduit 62 and into the interior of the mandrelnear the forward end thereof a flows rearwardly through the mandrel l4,coupling 41, mandrel bar 15 and coupling member 43 to also be dischargedthrough the fitting 63. Fluid such as water is supplied to the swivelfitting 63 through a conduit 64 and fluid is discharged through aconduit 65. Both of these are preferably flexible or are connected toflexible members so that the carriage can move along its path withoutdisturbing the fluid connections. While only the cooling fluidconnection is shown in the drawings, it will be evident that a lubricantcan also be supplied through an appropriate conduit as in my copendingapplication, aforesaid. Preferably, the lubricant conduit is disposedwithin the cooling liquid conduit as disclosed in that application.

Mandrel Movement Control: As noted above, the movement of the mandrelduring the actual rolling operation is controlled and substantialtension forces exerted on the mandrel bar 15 and thence the carriage 16are taken by the mandrel movement control beam 19 because the forwardend of the carriage 16 engages the shock absorbing pads 61 on the rearside of the mandrel movement control beam 19 during the rollingoperation. As shown particularly in FIGSJB, 1C, 23 and 2C, the mandrelmovement control beam 19 is a massive member that is supported byrollers 67 that operate on the tracks 42 of the inlet table extension18. The beam 19 has a central aperture through which the mandrel 14 andthe mandrel bar 15 can pass and the ends of the beam on the front sideare engaged by the piston rods 68 of the pistons within the massivehydraulic cylinders 69, these being suitably supported immediately tothe rear of the inlet table 13. The operation of the hydraulic cylindersis described below in the conjunction with the hydraulic circuit diagramas shown in FIG. 14. It will be evident, however, that by controllingthe flow of fluid to' and from the cylinders 69 the speed of movement ofthe mandrel 14 and mandrel bar 15 can be controlled and the forcesexerted on the mandrel during the rolling operation can be transmittedthrough the piston rods and the cylinder mechanism to the frame of themachine. The arrangement is such that the mandrel can be advanced orretracted'and the speed in either direction controlled both during eachrolling operation and between successive rolling operations so long asthe mandrel thrust block 16 is in contact with the mandrel movementcontrol beam 19.

Mandrel Rotating Mechanism: As in my copending application and asdescribed below, the movement of the mandrel during the rollingoperation is controlled to distribute the zones of wear longitudinallythroughout a substantial area of the mandrel. In order to eliminateconcentration of wear and high stress in circumferentially spaced zones,according to the present invention the mandrel is rotated, preferablyafter each rolling operation. A preferred mechanism for accomplishingthis is associated with the carriage l7 and is illustrated in FIGS. 4 to7.

As there shown, a ratchet wheel 71 is rigidly secured to the rear end ofcoupling member 43 of the carriage 17. The teeth of the wheel areengaged by a pawl'72 pivotally mounted on a ratchet lever or arm 73 thatis mounted for oscillatory movement concentric with the ratchet-wheel71. The pawl 72 is urged toward the center of ratchet wheel 71 by aspringpressed plunger 74 that is also carried by the ratchet arm orlever 73.

In order to rotate the ratchet wheel 71 and thus the mandrel bar 15 andmandrel 14 in the direction shown by the arrow in FIG. 6, a plunger 76that engages a pin 77 also carried by the ratchet arm 73 is provided.The plunger 76 is suitably guided in the carriage I7 and the lower endof the plunger 76 is engaged by a cam follower 78 that is supported byan arm 79 pivotally mounted on the carriage as at 80. The 'cam follower78 has a roller 81 that rides upon a track 82 having a cam portion 83,the track 82 being positioned adjacent one of the tracks 42 of the inlettable extension 18. It will be evident that when the carriage moves in arearward direction, the plunger 76 is raised by the cam follower 78 tothe dotted line position as shown in FIG. 7 when the roller 81 rides onthe cam portion 83 of the track 82, and then the pawl 72 rotates'theratchet wheel 71, mandrel bar and mandrel a fraction ofa turn. When thecarriage moves forwardly again toward the mill, the roller 81 rides fromthe elevated portion 84 of the track 82 down the cam portion 83 to thelower portion 85. As this takes place, the weight of the arm 73,assisted by a spring 86, rotates the arm 73 in the direction opposite tothe direction of the arrow in FIG. 6, placing the ratchet mechanism incondition for another fractional rotation of the ratchet wheel 71,mandrel bar 15 and mandrel 14 when the carriage 17 is again retractedand the wheel 81 rides upwardly on the cam portion 83.

The cam portion 83 is positioned near the rearward limit of the movementof the carriage 17 as indicated in FIG. 1C so that the mandrel will becompletely withdrawn from the mill and the workpiece at the time that itis rotated. The amount of rotation can be varied by varying thedifference in elevation between the portions 84 and 85 of the track 82so that, for example, the amount of rotation can be varied between thespacing of l, 2 or 3 teeth of the ratchet wheel 71.

By this simple and reliable mechanism that requires no attention on thepart of the operator, the mandrel is automatically rotated after everyworkpiece is passed through the mill. This rotation distributes the wearand stress circumferentially around the mandrel, distributes the heatingeffects on the mandrel and results in longer mandrel life and improvedrolling conditions.

Tube Pusher: In order to feed the workpieces W ,into the rolls 6' of thefirst roll stand 6 of the mill 5, atube pusher indicated in general at20 is disposed adjacent the inlet table l3 as shown in FIGS. 18, 2B and8. The mechanism comprises a carriage supported by two pairs of rollers91 that operate between upper tracks 92 and lower tracks 93 that extendparallel to the inlet table above the axis of the workpiece disposed onthe table and are supported by brackets 94 which are in turn supportedby the longitudinal member 95 of the inlet table 13.

The pusher itself is shown at 96 and comprises a rigid structurefabricated from plates welded together that extends downwardly from thecarriage 90 to a region adjacent the centerline of the apparatus asshown in FIG. 8. As there indicated, the lower end of the pusher 96 hasan arcuate recess 97 in it that is large enough to receive the mandrel14 and the mandrel bar and permit longitudinal movements of these partswithout interference. The aperture, however, is such that it will engagethe end of a workpiece supported on the inlet table 13 and thus theworkpiece can be moved or pushed into the bite of the rolls 6 byactuating the pusher from its retracted position toward the mill.

Movement of the pusher is accomplished by means of a hydraulic cylinderand piston mechanism 98 disposed above the hydraulic cylinders 69 thatcontrol the movement of the mandrel movement control beam 19 and have apiston rod 99 that is secured to the carriage 90. By means ofappropriate conventional controls, hydraulic fluid is supplied tocylinder 98 to urge the carriage 90 to the right, as shown in FIG. 2B sothat the pusher 96 engages the rear end of a tubular blank or workpieceto feed the leading end of the blank into the bite of the rolls 6' ofthe mill. After this is accomplished the hydraulic connections arereversed and the pusher is returned to its retracted positionsubstantially as shown in FIG. [B where it is ready for the nextoperation after the mandrel has been retracted and a new pierced shellor workpiece deposited on the inlet table 13.

Quick Change Mandrel: The mandrels used with the mill are subject towear and must periodically be replaced for this reason. Also, themandrels control the internal diameter of the tube rolled on the milland therefore whenever it is desired to roll tubing of difi'erent wallthicknesses or different internal diameters, replacement of the mandrelis required. Therefore, it is important that changing of the mandrels beaffected in the shortest period of time to reduce downtime of theapparatus A preferred form of construction for quickly connecting ordisconnecting the mandrel 14 to the mandrel rod 15 is shown at 41 andillustrated in FIGS. 10, 11, 12 and 13. a

As there shown this is a connection of the bayonet type with a femalecoupling member 101 threaded to the mandrel bar 1 and a male couplingmember 102 threaded to the mandrel 14 as shown at 103 and 104,respectively. The coupling member 101 has the same external diameter asthe mandrel rod 15 and this diameter is preferably equal to the externaldiameter of the smallest mandrel 14 to be used in the apparatus. Eachmandrel is provided with its own coupling member 102 and the couplingmember 101 remains permanently affixed to the mandrel bar 15. Thecoupling 101 is slotted as shown at 106 in FIG. 13 and is provided withintervening lugs 107. The coupling 102 has a sleeve portion 108 andspaced end lugs 110 which lie behind the lugs 107 of the female coupling101 when the parts are assembled as shown in FIG. 11. The couplingmembers are made of high-strength steel that is much stronger than theless expensive steels utilized in the mandrel and mandrel bar. The useof the high-strength steel makes possible the employment of abayonet-type joint.

In order to eliminate lost motion or play in the coupling, a wedgemember 109 is provided which has sloping surfaces 11 1 as shown in H6.12 that engage corresponding sloping surfaces on the ends of the lugs110 of the male coupling 102. The wedge member 109 is held againstrotation by a pin 112 engaged within an aperture 113 in the base 114 ofthe recess in the female coupling member 101. Three different openings113 are provided in the base 114 so that the angular position of thewedge member 109 can be varied. The parts are assembled in the usualmanner of a bayonet coupling by inserting the member 102 into the member101 and then turning the members relative to each other to bring thelugs 110 in back of the lugs 107 as shown. When this is done the endsurfaces of the lugs ride on the sTo'pTrig surface 111 of the wedgemember 109 and with the wedge member properly positioned take up alllongitudinal play between the two coupling members 101 and 102. If theadjustment provided by the pins 112 and apertures 113 is insufficientshims can be employed between the wedge member and the base 114. Afterassembling, the parts are held against accidental rotation by means of akey 115 that is secured to the coupling member 102 by a screw 116 andengages within a recess 117 in the external surface of the couplingmember 101.

As previously explained, there is a cooling fluid conduit 62 within themandrel bar and mandrel. This is made up ofa portion 62a carried by themandrel l4 and a portion 62b carried by the mandrel bar 15. The ends ofthese conduit portions are centered accurately within the couplingmembers 101 and 102 by spacers 118 and 119, respectively. A femalecoupling member or fluid connector 120 is secured to the end of conduit62b as by welding or brazing and a male coupling member 121 is similarlysecured to the end of the conduit section 620. These parts interfit asshown in FIG. 11 when the mandrel is coupled to the mandrel rod, a sealautomatically being provided by an O-ring or similar sealing member 122.Since there is not substantial pressure, in the returning fluid flowingaround the exterior of the conduit 62 no external seal is providedbetween the coupling members 101 and 102 but, if desired, O-rings can beincorporated in these connections also.

It will be evident that with the foregoing arrangement the 'mandrel 14can be disconnected from the mandrel bar 15 simply. by removing the key115, rotating the parts with respect to each other about 60 andwithdrawing the mandrel and its coupling 102 from the mandrel barcoupling member 101. This automatically disconnects the cooling fluidconduit sections 62a and 62b. The mandrel is then removed from the millor'the apparatus, a new mandrel placed in position and the assemblycompleted by inserting the coupling 102 of the new mandrel into thecoupling 101 of the mandrel bar and rotating the parts 60 in theopposite direction to complete the bayonet coupling. The wedge memberhaving been properly positioned to eliminate play and then the key 115is replaced to lock the parts securely together. By this means mandrelscan be interchanged in a comparatively short period of time, forexample, a matter of a few minutes. This makes an important contributionto the efficient operation of the apparatus and to the operation of theentire tube manufacturing facility by the reduction of downtime.

- Hydraulic Circuit for Mandrel Movement Control Beam: It will beevident that by appropriate control of the flow of hydraulic fluid toand from the opposite ends of the doubleacting cylinders 69 the movementof the mandrel control beam 19 and hence movement of the mandrel at alltimes that the mandrel thrust block 16 is in engagement with the beam 19can be readily affected. A simplified hydraulic circuit for obtainingsuch control is shown in FIG. 14.

As there indicated the cylinders 69 are double-acting, each containing apiston 68athat is connected to its associated piston rod 68 rigidlysecured to the mandrel movement control beam 19. The hydraulic systemcomprises a motor 123 that drives a pump 124 that supplies fluid underpressure, preferably water, for operating the system. The pump 124 isconnected through suitable lines as shown, a two-way solenoid valve 125,an adjustable flow control valve 126 and line 132 to the rearward endsof the cylinders 69. A pressure relief valve 128 and a solenoidunloading valve 129 are interposed in the line between the pump 124 andthe solenoid valve 125. The pump 1 24 is also connected to anaccumulator 139 through lines as shown, a shutoff valve 138 and a checkvalve 136.

The accumulator 139 is also connected to the forward ends of thecylinders 69 by suitable lines as shown, a solenoid valve 140, anadjustable flow control valve 141, another solenoid valve 142, andanother flow control valve 144. A pressure relief valve 143 is alsoconnected to the lines between the accumulator 139 and the forward endsof the cylinders 69.

At the start of the rolling cycle suitable control devices such as alimit switch energizes solenoid 130 of solenoid valve 125 to connect thepump 124 to the rearward ends of the cylinders 69 wherein the pistons68a are in their rearward positions opposite that shown in FIG. 14.Solenoid valve 129 is energized to prevent flow to its sump and solenoidvalve 142 is also energized to permit flow of fluid out of the forwardends of the cylinders 69 through the appropriate lines to theaccumulator 139. This supplies pressure to the rod ends of the cylindersto accelerate the mandrel control beam 19 and mandrel 14 to theappropriate starting velocity which velocity can be controlled by theflow control valve 144 between the forward ends of the cylinders 69 andthe solenoid valve 142. As soon as the work? piece W is gripped by themill stand 6, appropriate controls such as relays initiate thedeenergizing of solenoid'130 of solenoid valve 125 and energize solenoid131 of valve 125 to release the supply pressure from the pump 124 to therearward or rod ends of the cylinders 69, the fluid then being,

opened to the sump of valve 125. At the same time the solenoid valve No.129 is deenergized to unload the pump 124. Solenoid valve 142 isdeenergized thereby forcing all of the fluid from the hydrauliccylinders 69 through the flow control valve 141 which controls themovement of fluid fromthe forward ends of the cylinders 69 to theaccumulator 139 thereby controlling the movement and velocity of themandrel. During this operation the solenoid valve 140 is deenergized.Other means, such as a variable displacement hydraulic pumpor' motor canbe utilized for metering the flow of fluid from the cylinders, therebyto control the speed of the mandrel.

Pressure relief valves 128 and 143 are provided on appropriate sides ofthe hydraulic cylinders 69 to relive pressure in the event of undesiredpressure buildup within the lines. As the pistons 68a approach theirpositions as shown in FIG. 14, pressure builds up in the gas-chargedaccumulator 139 which is charged with air at its upper end from asuitable source of PP y- At the end of the rolling cycle suitablecontrols such as. a

heat-sensing switch will initiate the return of the piston rod 68;

and associated structure to the appropriate position to receive a secondworkpiece for start up of a second cycle. The appropriate controlenergizes the solenoid valve 140 to supply pressure from the chargedaccumulator 139 to theforward ends of the cylinders 69 for rapid returnto the startup position. The velocity of the return is controlledby the.adjustable control valve 126 connected by lines 132 to the rearwardends of the cylinders 69. An appropriate control is energized'bythecylinders piston rods 68 upon their return to the substantial resetposition which deenergizes the solenoid. valve 140 thereby blockingfurther flow of fluid from the accumulator 139. At the same time theappropriate device actuates the flow restrictor valve 134.

If a stripping cycle is indicated because the workpiece has stuck to themandrel [4, suitable controls deenergizesolenoid 131 and energizesolenoid 130 of valve 125, solenoid valve 129 and solenoid valve 142.This prevents rearward movement of the piston rods 68 and mandrelcontrol beam- 19 and mandrel 14 until the workpiece has cleared thestripper plate 22 at which time the solenoid 130, the solenoidvalve 1'29and 142 are deenergized thereby permittingrearward movement of thepiston rods 68 thereby withdrawing the mandrel from within the workpiecewhose rearward motion is restricted by the stripper plate 22.

At the rear end of the cylinders 69, cushioning chambers 135 areprovided, these cooperate with the projections 137 on the pistons 68a tocushion the end ofthe return stroke of the pistons 68a. The normal flowof fluid out of the cylinders 69 is through the line 132 directly to anadjustable remotely controlled flow control valve 126 while after theprojections 137 have reached the recesses or chambers 135 the flow musttake place through the flow-restrictor 133, there, being a check.

valve 134 in parallel with the restrictor 133 so that flow of fluidintothe cylinder at the rear ends thereof can taken place freely..

It will be evident that witmm'rangement of this sort the movement of thebeam 19, and hence the mandrel 14 and the mandrel bar 15 can becontrolled in either direction. Thus, the mandrel can be advanced beforeit is in the mill and after the mandrel thrust block 16 has come intocontact with the mandrel control beam 19 by admitting fluid underpressure to the rear end of the cylinders 69 and controlling the rate ofdischarge of the fluid from the forward ends of the cylinders throughthe flow control valve 144, the cable mechanism associated with themandrel carriage 17 maintaining the mandrel thrust block 16 inengagement with the beam 19 during this time.

After the rolling operation has been initiated the frictional engagementbetween the rapidly advancing shell and the mandrel exerts a strongadvancing force on the mandrel and hence on the mandrel bar 15, thrustblock 16and beam 19. The rate of advance then is controlled by theadjustable flow control valve 141.The rate of retraction is controlledby the fluid flow control valve 126. This movement is also useful in theevent that a tubular shell should stick to the mandrel and it becomesnecessary to strip the shell from the mandrel using the stripper 22.Thus, the hydraulic system can be employed to give great flexibility ofoperation and control over the movement of the mandrel whenever themandrel thrust block is in engagement with the mandrel movement controlbeam 19. This flexibility of operation will-become more apparent uponconsideration of the description of the operation of the apparatusthatfollows.

Operation and Control: A typical sequence of operations of the apparatusis shown in FIGS. 15 to 19 and these figures also illustrate preferredinstrumentation to give the .operator at'the control console accurateknowledge of the relative positions of the workpiece W and mandrel 14 atall times. FIGS. 20 to 23 show particular stages of the rolling cycleand the velocity diagrams, FIGS. 24 and 25,v show the relative speedsor-veloci ties of the workpiece and the mandrel of plug during therolling operation. 5

ln FIGSI 15 to 19 the operator's instrument panel is indicateddiagrammatically at 145. This is positioned on the console at which thecontrols for the various instrumentalities are located and includes ahousing having a series of lights 146 which are illuminated to show theposition of the workpiece,

and a window 147 behind whichan indicator 148 showingthe position of themandrel 14 is disposed. The indicator moves across the window inresponse to movement of the mandrel, the movement. of the indicatorbeing controlled by an appropriate servomeehanism diagrammaticallyindicated at 149 so that a corresponding light l46-is illuminatedwhenever a heated shell-is opposite its associated heat-sensing device150; Thus, the lights 146 light. up-progressively as the shell isadvanced toward and through the mill. In the drawinglighted lamps areindicated by clear circles, unlighted lamps have an x in their centers.It is to be understood, of course, that the instrument is drawn to anentirely different scale from the diagrams constituting FIGS. 15. to 19.

It is also to be noted that in FIGS. 15 'to 19 while most of theelements of the machine are indicated in plan; some parts such as theroll stands, the pusher and the supporting idler rolls are indicated inelevation for.convenience of illustration.

A typical sequence of operation is as follows.- ln FIG. 15 a workpiece.W in. the form of a pierced billet has been deposited indicate thepresence of the workpiece or shell in position as will be seen by theillumination of the corresponding lights 146. The mandrel 14 isretracted to a position about opposite the tube pusher 20 to make roomfor the depositing of the workpiece W on the inlet table 13 and the endof the mandrel is shown by the indicator 148 as being in its retractedposition. In FIG. 16 the mandrel stop 35 has been moved out of the wayand the workpiece W has been pushed into the bite of the first rollstand 6 as shown, this being indicated by the lighting of the light 146immediately in advance of the first roll stand 6 and the extinguishingof the first light 146, showing the movement of the trailing end of theworkpiece toward the mill. The mandrel thrust block 16 is in engagementwith the mandrel move ment control beam 19 and the mandrel itself .hasbeen projected until its end is just beyond the fourth roll stand 9. Thelines on the window of the instrument 145 indicate the centerlines ofthe roll stands and thus the operator can see at a glance the positionof the mandrel 14 with respect to the mill and also the location of theworkpiece. In FIG. 17 the mandrel has been advanced to a point justbeyond the last roll stand I 1, in which the tube is rounded up, againas indicated by the indicator, l48, while the last three lights 146 areilluminated to show the presence of the trailing end of the workpiecenear the delivery end of the mill. The first several lights have beenextinguished indicating that the trailing end of the workpiece haspassed beyond these stations. The lights are successively extinguishedas the trailing end of the workpiece advances.

In FIG. 18 the mandrel has been advanced to the full limit of its travelwhich is ordinarily done only in the case of a sticking workpiece andthe indicator shows that the point of the mandrel is beyond the stripper22, while all of the lights are extinguished indicating that theworkpiece is beyond the mill. Under these circumstances the operatoractuates the stripper to position it as shown in FIG. 18 to blockretracting move ment of the workpiece toward the mill and then fluidunder pressure is admitted to the cylinders 69 to withdraw the man drelfrom the workpiece. Normally this is not required, the mandrel isadvanced only to the position shown in FIG. 17 and then isretracted assoon as the workpiece has passed the last working roll stand 9.

The apparatus is placed in position for another operation by retractingthe mandrel to its initial position as shown in FIG. 19 and as indicatedby the position of the indicator 148. The inlet table is then ready toreceive another workpiece with the shell stop 35 in position. Theabsence of a workpiece on the inlet table 13 is indicated by the factthat all of the lights 146 are extinguished.

FIGS. 20, 21, 22 and 23 show in greater detail the relative positions ofthe workpiece and mandrel during a typical rolling operation includingstripping of the workpiece from the mandrel 14 and FIG. 24 shows thespeed of the workpiece at various positions in the mill while FIG. 25shows the location of a point on the mandrel and the speed of anddirection of movement of the mandrel when the point is located as shown.

In FIG. 20 the leading end of the workpiece is at point in advance ofthe first roll stand. The workpiece is accelerated by the pusher throughthe segment a of the curve constituting FIG. 24 to an entering speed VTEwhich is just a little less and could be the same as the surface speedVR6 which is the surface speed of the rolls 6 of the first roll stand 6.The workpiece entering the first roll stand 6 is rapidly accelerated sothat its speed equals the speed of the roll stand but because of theelongation that takes place in the roll stand the workpiece leaving theroll stand is accelerated to a speed VR7 which corresponds quite closelyto the speed of the rolls 7' in the second roll stand 7. The rolls beingdesigned so that the rolls in each succeeding stand have a surface speedthat is approximately equal to the calculated speed of the leading endof the.

workpiece as it enters the rolls thus to minimize shock on theequipment.

The workpiece is again elongated as it passes through the rolls 7 andthe speed again increases to the speed indicated at FIG. 25 shows apreferred mode of operation with respect to control of the speed of themandrel 14. In FIG. 20 the mandrel has entered to the point shown withits leading end beyond the third roll stand 8. A point P on the mandrelis selected for reference in this discussion. The mandrel is stationaryand the work is stationary. As the workpiece is pushed into the firstroll stand 6 by the pusher 20 the hydraulic con- "trol apparatus of FIG.14 is operated to advance the mandrel by a distance d, which brings thepoint P to a point approximately even with the leading end of theworkpiece as shown in FIG. 21, and with the mandrel moving at a velocityVME which is substantially equal to the entering velocity VTE of theworkpiece into the first roll pass which preferably is substantiallyequal or slightly below the speed VR-6 which is the lineal speed of therolls in the first roll pass. In either event, the entry of theworkpiece into the first roll pass is greatly facilitated and shock onthe mandrel 14 on the mill and on the mechanism of the entire apparatusis greatly reduced. The acceleration of the mandrel'is shown by thesloping portion A of the curve of FIG. 25.

After the workpiece has entered the first roll stand the mandrel isslowed down as shown by the sloping portion b of the curve of FIG. 25and then continued at a substantially uniform velocity as indicated by cthrough a major portion of the rolling period of the tube whereupon themandrel is stopped after having been move through a distance d; to theposition shown in FIG. 22. The velocity c is determined by the length ofthe workpiece thelength of the mandrel and the amount of elongationtaking place in the mill being calculated so that the mandrel willalways be present to support the workpiece wherever reduction andelongation of the workpiece takes place. Withdrawing movement of themandrel is then started immediately as shown by the curve 2, thepresence of the mandrel not being required in the last roll stands 10and 11 since their function is primarily to round up the work and stripit from the mandrel. If the workpiece does not stick to the mandrel,retraction as shown by the curve e is continued and the mandrel iswithdrawn to its original position as shown in FIGS. 15 and 19.

However, if the tube sticks to the mandrel in the position shown in FIG.22, then the mandrel is advanced through the distance d, while thetrailing end of the workpiece is advanced through a correspondingdistance w as shown in FIG. 23 so that the trailing end of the workpieceis beyond the stripper plate 22. This operation is shown by the portionf of the curve in FIG. 25 which indicates movement of the mandrel in theforward direction along with the blank and reduction of movement of theforward motion to 0 at point g. The mandrel is then accelerated in therearward direction as at h with continued movement in a rearwarddirection at a fairly low velocity 1' until the mandrel is released fromthe sticking tube. Then acceleration in the reverse direction is asshown at j and continued high-speed retraction at a fairly high velocityk until the original position indicated in FIGS. 15 and 19 is reached.

The foregoing description of operation is given as an example of thepreferred operation that is possible with the present construction andin which the mandrel is advanced at approximately the entry speed of thefirst roll stand, at the moment that the workpieceis entered into thefirst roll stand. This is highly advantageous because of the reductionin shock to the apparatus. However, it will be understood that becauseof the nature of the controls, difierent modes of operation can beutilized with the apparatus to conform to working conditions and thematerials being rolled. It will be evident that the knowledge given tothe operator of the location of the shell or workpiece and the locationof the mandrel with respect to it gives him an important tool inproperly controlling the workpiece and the rolling operation. Byobservation at his console he can determine these positions with asufiicient degree of accuracy to enable him to vary the control of anddirection of movement of the mandrel-if that seems advisable. This canbe accomplished through the hydraulic control system even though therelative positions of the workpiece and the mandrel would be invisibleto him otherwise, because the leading end of the mandrel, is, of course,concealed within the workpiece while the portion of the workpiece itselfthat is within the mill cannot be accurately observed.

Various changes and modifications in the method and apparatus may bemade without departing from the spirit and scope of the invention, apreferred form of which has been described herein. The essentialcharacteristics of the invention are defined in the appended claims.

Iclaim: l. The method of rolling a tubular blank to elongate it andreduce its diameter which includes the steps of disposing the blank onthe entry side of a mill having a plurality of roll stands havinggrooved rolls providing passes of progressively reduced diameter,passing an elongated mandrel through the blank and into the pass of themill, feeding the blank into the first roll stand of the mill, rollingthe blank continuously through the mill over the mandrel, moving themandrel in a axial direction with respect to both the mill and the blankduring substantially the entire rolling operation, discharging therolled blank on the exit side of the mill, and withdrawing the mandrelto the inlet side of the mill a distance sufficient to permitanothe:blank to be positioned between the forward end of the mandrel and themill, the improvement which comprises moving the blank into the firstroll stand independently of the mandrel at a speed equal to or slightlyless than the lineal speed'of the rolls in the first roll stand, andmoving the mandrel in ;the same direction as the blank and at a speedthat, at the instant that the blank enters the first roll stand, is alsoequal to or slightly less than the lineal speed of the rolls in thefirst roll stand, therebj; to reduce shock on the mandrel at the timethat the blank enters the mill, and substantially reducing the speed ofmovement of the mandrel immediatelyafter the blank has entered the firstroll stand.

2. Apparatus for rolling tubular blanks comprising a mill embodying aplurality of aligned rolls stands adapted 'to reduce the tubular blankpassing therethrough, an inlet table at the entry end ofthe mill forsupporting a tubular blank to be rolled, an elongated mandrel adapted tosupport a blank being rolled in the mill, a mandrel bar extendingrearwardly from the mandrel for controlling the position and movement ofthe mandrel means for controlling the speed and direction of movement ofthe mandrel bar during the rolling operation, a

pusher operable independently of the mandrel bar for pushing a tubularblank disposed on said inlet table into the first of the plurality ofroll stands and means independent of the pusher for advancing themandrel bar and mandrel at the time that the leading end of the tubularblank is pushed into the first roll stand of the mill.

3. An apparatus for rolling tubular blanks comprising a continuous millembodying a plurality of aligned roll stands, each roll stand having atleast two rolls defining a roll pass, an inlet table at the entry end ofthe mill for supporting a tubular blank to be rolled in alignment withthe working pass of the mill, a mandrel adapted to support the interiorof a blank being rolled, said mandrel being movable from a retractedposition spaced from the mill sufficiently to permit a blank to berolled to be deposited on said inlet table between the forward end ofthe mandrel and the mill and a position in which the forward end of themandrel projects through the mill, a mandrel bar secured to andextending rearwardly from the mandrel for controlling the position andmovement of the mandrel, power means for positively controlling theposition and movement of said mandrel bar, said power means being undercontrol of the operator, and indicating means visible to the operatorfor indicating the position of the mandrel with respect to the mill atall times during the operation of the apparatus.

4. Apparatus according to claim 3 in which the mandrel bar is supportedby a carriage that operates toward and away from the mill and theindicating means is controlled by a servomechanism interconnecting thecarriage and the indicating means.

5. Apparatus according to claim 3 having means for indicating theposition of a tubular blank with respect to the mill during theoperation of the apparatus.

6. Apparatus according to claim 5 in which the means for indicating theposition of the tubular blank and the means for indicating the positionof the mandrel are displayed on the same panel whereby the relativepositions of the mandrel and blank are exhibited to the operator duringthe operation of the apparatus.

7. Apparatus according to claim 5 wherein a series of heatsensingdevices are employed to control the means for indicating the position ofthe tubular blank.

8. In an apparatus for rolling tubular blanks on a continuous rollingmill embodying a plurality of aligned rolls stands and having a mandreladapted to support the interior of a blank being rolled in the mill anda mandrel bar for controlling the position and movement of the mandrel,the mandrel being subjected to tension during the rolling operation, theimprovement which comprises the provision of means for effecting rapidinterchange of one mandrel for another without changing the mandrel barwhich comprises a fitting secured to the rear end of the mandrel and afitting secured to the forward end of the mandrel bar, said fittingshaving diameters-not in excess of the diameters of the smallest mandrelto be used on the mill, and said fittings beingprovided withinterengaging mating parts to provide a bayonet-type joint whereby thefittings can be quickly connected and disconnected from each other,thereby to correspondingly disconnect and connect a mandrel from themandrel bar, there being a wedge member having inclined faces disposedwithin one of said fittings and the end of the other of said fittingshaving corresponding inclined faces adapted to engage the inclined facesof the wedge member, whereby when the mandrel bar and mandrel arerotated with respect to each other to complete the locking of thebayonet joint the engagement of said inclined surfaces eliminateslongitudinal play from the joint.

9. Apparatus according to claim 8 in which the mandrel bar and mandrelare tubular and in which there is a fluid conduit disposed coaxiallywith the mandrel bar and mandrel, said fluid conduit being divided intotwo parts, one part carried by the mandrel bar and the other partcarried by the mandrel, there being fittings on the adjacent ends of thetwo parts whereby a fluidtight connection is automatically made when thebayonet connection between the fitting on the mandrel and the fitting onthe mandrel bar is completed.

10. Apparatus according to claim 9 in which one part of said conduit isprovided with a male fitting and the other part of the conduit isprovided with a female fitting, the said fittings being disposed onewithin the other when the mandrel and mandrel bar are connectedtogether, there being a seal between said fittings when the mandrel andmandrel bar are connected together.

11. Apparatus as defined in claim 10 in which the seal is an O-ringdisposed in a groove in one of said fittings and engaging a cylindricalsurface on the other of said fittings.

12. An apparatus for rolling tubular blanks comprising a continuous millembodying a plurality of aligned roll stands, each roll stand havinggrooves defining a roll pass adapted to reduce a blank passingtherethrough, an inlet tube disposed at the entry end of the mill forsupporting a tubular blank to be rolled in alignment with the workingpass of the mill, a mandrel adapted to support the interior of a blankrolled in the mill, a mandrel bar for controlling the position andmovement of the mandrel, the forward end of the mandrel bar beingsecured to the rear end of the mandrel, a mandrel thrust block securedto the rear end of the mandrel bar, a carriage supporting the mandrelthrust block and supported on tracks on an inlet table extension formovement in directions toward and away from the mill parallel to thepass line of the mill, drive means for operating said carriage towardand away from the mill on said tracks, said means comprising a flexibleelement supported adjacent said tracks and having its ends secured tosaid carriage, a motor for driving said flexible element in eitherdirection, said drive means including means adapted to exert asubstantial torque urging the carriage, mandrel bar and mandrel in adirection toward the mill even through there be no movement of thecarriage, said mandrel thrust block, mandrel bar and mandrel beingretracted to permit a blank to be rolled to be deposited on the inlettable between the forward end of the mandrel and the mill, said carriagebeing movable toward said mill to move said mandrel through a blankpositioned on said inlet table and to project said mandrel into theworking'pass of the mill, means associated with the carriage forrotating the mandrel bar and mandrel a fraction of a turn each time themandrel is moved to its retracted position, a mandrel movement controlbeam engageable with the mandrel thrust block whereby the mandrelmovement control beam can apply forces to the mandrel thrust block inopposition to the forces exerted on the mandrel during the rollingoperation, hydraulic cylinder means for controlling the movement of saidmandrel movement control beam comprising at least one double-actinghydraulic cylinder secured to said mandrel movement control beam, asource of hydraulic fluid under pressure, a hydraulic circuitcontrollable to selectively supply fluid under pressure to either end ofsaid cylinder thereby to apply forces to move said mandrel movementcontrol beam toward the mill or away from said mill selectively, fluidflow control means associated with each end of said cylinder adapted tocontrol the discharge of hydraulic fluid of movement of said mandrelmovement control beam in either direction, a movable stop adapted toengage the forward end of a tubular blank disposed on said inlet tableand restrain movement of the blank toward the mill during the time thatthe mandrel is advanced through the blank into the mill, said stop beingmovable out of the path of the blank to a permit the blank to enter themill, a pusher adapted'to engage I the rear end of the tubular blankdisposed on the mill and push the blank into the bite of the rolls ofthe first roll stand of the mill, and a hydraulic cylinder mechanism,.for advancing and retracting said pusher. v

13. Apparatus according to claim 12 having a stripper plate disposedbeyond the exit end of the mill, said stripper plate being movable froman inactive position where it permits passage of a blank from the millto a support disposed beyond the mill to an active position in which itwill block movement of a blank on said outlet table toward the millwhile permitting movement of the mandrel toward the mill whereby themandrel may be withdrawn from a blank by operation of the mandrelmovement control beam in the direction away from the mill.

14. Apparatus according to claim 12 having indicating means visible tothe operator for indicating the position of the mandrel with respect tothe inlet table and the mill and indicating means also visible to theoperator for indicating the Y position of a tubular blank with respectto'the mill during the operation of the apparatus.

1. The method of rolling a tubular blank to elongate it and reduce itsdiameter which includes the steps of disposing the blank on the entryside of a mill having a plurality of roll stands having grooved rollsproviding passes of progressively reduced diameter, passing an elongatedmandrel through the blank and into the pass of the mill, feeding theblank into the first roll stand of the mill, rolling the blankcontinuously through the mill over the mandrel, moving the mandrel in aaxial direction with respect to both the mill and the blank duringsubstantially the entire rolling operation, discharging the rolled blankon the exit side of the mill, and withdrawing the mandrel to the inletside of the mill a distance sufficient to permit another blank to bepositioned between the forward end of the mandrel and the mill, theimprovement which comprises moving the blank into the first roll standindependently of the mandrel at a speed equal to or slightly less thanthe lineal speed of the rolls in the first roll stand, and moving themandrel in the same direction as the blank and at a speed that, at theinstant that the blank enters the first roll stand, is also equal to orslightly less than the lineal speed of the rolls in the first rollstand, thereby to reduce shock on the mandrel at the time that the blankenters the mill, and substantially reducing the speed of movement of themandrel immediately after the blank has entered the first roll stand. 2.Apparatus for rolling tubular blanks comprising a mill embodying aplurality of aligned rolls stands adapted to reduce the tubular blankpassing therethrough, an inlet table at the entry end of the mill forsupporting a tubular blank to be rolled, an elongated mandrel adapted tosupport a blank being rolled in the mill, a mandrel bar extendingrearwardly from the mandrel for controlling the position and movement ofthe mandrel, means for controlling the speed and direction of movementof the mandrel bar during the rolling operation, a pusher operableindependently of the mandrel bar for pushing a tubular blank disposed onsaid inlet table into the first of the plurality of roll stands andmeans independent of tHe pusher for advancing the mandrel bar andmandrel at the time that the leading end of the tubular blank is pushedinto the first roll stand of the mill.
 3. An apparatus for rollingtubular blanks comprising a continuous mill embodying a plurality ofaligned roll stands, each roll stand having at least two rolls defininga roll pass, an inlet table at the entry end of the mill for supportinga tubular blank to be rolled in alignment with the working pass of themill, a mandrel adapted to support the interior of a blank being rolled,said mandrel being movable from a retracted position spaced from themill sufficiently to permit a blank to be rolled to be deposited on saidinlet table between the forward end of the mandrel and the mill and aposition in which the forward end of the mandrel projects through themill, a mandrel bar secured to and extending rearwardly from the mandrelfor controlling the position and movement of the mandrel, power meansfor positively controlling the position and movement of said mandrelbar, said power means being under control of the operator, andindicating means visible to the operator for indicating the position ofthe mandrel with respect to the mill at all times during the operationof the apparatus.
 4. Apparatus according to claim 3 in which the mandrelbar is supported by a carriage that operates toward and away from themill and the indicating means is controlled by a servomechanisminterconnecting the carriage and the indicating means.
 5. Apparatusaccording to claim 3 having means for indicating the position of atubular blank with respect to the mill during the operation of theapparatus.
 6. Apparatus according to claim 5 in which the means forindicating the position of the tubular blank and the means forindicating the position of the mandrel are displayed on the same panelwhereby the relative positions of the mandrel and blank are exhibited tothe operator during the operation of the apparatus.
 7. Apparatusaccording to claim 5 wherein a series of heat-sensing devices areemployed to control the means for indicating the position of the tubularblank.
 8. In an apparatus for rolling tubular blanks on a continuousrolling mill embodying a plurality of aligned rolls stands and having amandrel adapted to support the interior of a blank being rolled in themill and a mandrel bar for controlling the position and movement of themandrel, the mandrel being subjected to tension during the rollingoperation, the improvement which comprises the provision of means foreffecting rapid interchange of one mandrel for another without changingthe mandrel bar which comprises a fitting secured to the rear end of themandrel and a fitting secured to the forward end of the mandrel bar,said fittings having diameters not in excess of the diameters of thesmallest mandrel to be used on the mill, and said fittings beingprovided with interengaging mating parts to provide a bayonet-type jointwhereby the fittings can be quickly connected and disconnected from eachother, thereby to correspondingly disconnect and connect a mandrel fromthe mandrel bar, there being a wedge member having inclined facesdisposed within one of said fittings and the end of the other of saidfittings having corresponding inclined faces adapted to engage theinclined faces of the wedge member, whereby when the mandrel bar andmandrel are rotated with respect to each other to complete the lockingof the bayonet joint the engagement of said inclined surfaces eliminateslongitudinal play from the joint.
 9. Apparatus according to claim 8 inwhich the mandrel bar and mandrel are tubular and in which there is afluid conduit disposed coaxially with the mandrel bar and mandrel, saidfluid conduit being divided into two parts, one part carried by themandrel bar and the other part carried by the mandrel, there beingfittings on the adjacent ends of the two parts whereby a fluidtightconnection is automatically made when the bayonet connection between thefitting On the mandrel and the fitting on the mandrel bar is completed.10. Apparatus according to claim 9 in which one part of said conduit isprovided with a male fitting and the other part of the conduit isprovided with a female fitting, the said fittings being disposed onewithin the other when the mandrel and mandrel bar are connectedtogether, there being a seal between said fittings when the mandrel andmandrel bar are connected together.
 11. Apparatus as defined in claim 10in which the seal is an O-ring disposed in a groove in one of saidfittings and engaging a cylindrical surface on the other of saidfittings.
 12. An apparatus for rolling tubular blanks comprising acontinuous mill embodying a plurality of aligned roll stands, each rollstand having grooves defining a roll pass adapted to reduce a blankpassing therethrough, an inlet tube disposed at the entry end of themill for supporting a tubular blank to be rolled in alignment with theworking pass of the mill, a mandrel adapted to support the interior of ablank rolled in the mill, a mandrel bar for controlling the position andmovement of the mandrel, the forward end of the mandrel bar beingsecured to the rear end of the mandrel, a mandrel thrust block securedto the rear end of the mandrel bar, a carriage supporting the mandrelthrust block and supported on tracks on an inlet table extension formovement in directions toward and away from the mill parallel to thepass line of the mill, drive means for operating said carriage towardand away from the mill on said tracks, said means comprising a flexibleelement supported adjacent said tracks and having its ends secured tosaid carriage, a motor for driving said flexible element in eitherdirection, said drive means including means adapted to exert asubstantial torque urging the carriage, mandrel bar and mandrel in adirection toward the mill even through there be no movement of thecarriage, said mandrel thrust block, mandrel bar and mandrel beingretracted to permit a blank to be rolled to be deposited on the inlettable between the forward end of the mandrel and the mill, said carriagebeing movable toward said mill to move said mandrel through a blankpositioned on said inlet table and to project said mandrel into theworking pass of the mill, means associated with the carriage forrotating the mandrel bar and mandrel a fraction of a turn each time themandrel is moved to its retracted position, a mandrel movement controlbeam engageable with the mandrel thrust block whereby the mandrelmovement control beam can apply forces to the mandrel thrust block inopposition to the forces exerted on the mandrel during the rollingoperation, hydraulic cylinder means for controlling the movement of saidmandrel movement control beam comprising at least one double-actinghydraulic cylinder secured to said mandrel movement control beam, asource of hydraulic fluid under pressure, a hydraulic circuitcontrollable to selectively supply fluid under pressure to either end ofsaid cylinder thereby to apply forces to move said mandrel movementcontrol beam toward the mill or away from said mill selectively, fluidflow control means associated with each end of said cylinder adapted tocontrol the discharge of hydraulic fluid from each end of said cylinderand thereby to control the rate of movement of said mandrel movementcontrol beam in either direction, a movable stop adapted to engage theforward end of a tubular blank disposed on said inlet table and restrainmovement of the blank toward the mill during the time that the mandrelis advanced through the blank into the mill, said stop being movable outof the path of the blank to permit the blank to enter the mill, a pusheradapted to engage the rear end of the tubular blank disposed on the milland push the blank into the bite of the rolls of the first roll stand ofthe mill, and a hydraulic cylinder mechanism for advancing andretracting said pusher.
 13. Apparatus according to claim 12 having astripper plate disposeD beyond the exit end of the mill, said stripperplate being movable from an inactive position where it permits passageof a blank from the mill to a support disposed beyond the mill to anactive position in which it will block movement of a blank on saidoutlet table toward the mill while permitting movement of the mandreltoward the mill whereby the mandrel may be withdrawn from a blank byoperation of the mandrel movement control beam in the direction awayfrom the mill.
 14. Apparatus according to claim 12 having indicatingmeans visible to the operator for indicating the position of the mandrelwith respect to the inlet table and the mill and indicating means alsovisible to the operator for indicating the position of a tubular blankwith respect to the mill during the operation of the apparatus.